Liquid blade pump

ABSTRACT

A pump includes: a rotor and a stator; the rotor having at least one liquid opening configured for fluid communication with a liquid source. The liquid opening is configured such that a stream of liquid is output to form a liquid blade between the rotor and the stator, and gas confined by the stator, the rotor and the liquid blade is driven through the pump . The pump is configured such that a pumping channel has side walls that slope towards each other from the rotor that comprises the liquid opening towards a further wall of the pumping channel remote from the rotor, such that a distance between the side walls decreases with increasing distance from the liquid opening, a tangent to a midpoint of the side walls having an angle of between 5° and 40° with respect to a line perpendicular to an axis of rotation of the rotor.

CROSS-REFERENCE OF RELATED APPLICATION

This application is a Section 371 National Stage Application ofInternational Application No. PCT/GB2021/052024, filed Aug. 5, 2021, andpublished as WO 2022/034291A1 on Feb. 17, 2022, the content of which ishereby incorporated by reference in its entirety and which claimspriority of British Application No. 2012474.9, filed Aug. 11, 2020.

FIELD

The field of the invention relates to pumps.

BACKGROUND

Different types of pumps for pumping gases are known. These includeentrapment type pumps, where a gas is captured on a surface inside thepump prior to being removed; kinetic or momentum transfer pumps such asturbomolecular pumps where the molecules of the gas are accelerated fromthe inlet side towards the outlet or exhaust side, and positivedisplacement pumps, where gas is trapped and moved from the inlettowards the outlet of the pump.

Positive displacement pumps provide moving pumping chambers generallyformed between one or more rotors and a stator, the movement of therotors causing the effective pumping chamber to move. Gas received at aninlet enters and is trapped in the pumping chamber and moved to anoutlet. In some cases the volume of the gas pocket reduces duringmovement to improve efficiency. Such pumps include roots, and rotaryvane type pumps. In order to draw the gas into the chamber, the chambergenerally expands and to expel the gas from the chamber, the chambervolume generally contracts. This change in volume can be achieved forexample in a rotary vane pump by blades that extend in and out of thepump chamber using devices such as springs, which are themselves subjectto wear, or using two synchronised rotors in a roots or screw pump whichcooperate with each other and a stator to move a pocket of gas andgenerate the volumetric changes between inlet and outlet. An additionalrotor requires an additional shaft, bearings and timing methods such asgears to synchronise the rotor movements.

Furthermore, in order to minimise or at least reduce leakage and movethe gas efficiently while it is trapped the moving parts need to form aclose seal with each other and with the static parts which form thetrapped volume of gas. Some pumps use a liquid such as oil to sealbetween the surfaces of the trapped volume whilst others rely on tightnon-contacting clearances which can lead to increased manufacturingcosts and can also lead to pumps that are sensitive to locking orseizure if the parts come into contact or where particulates orimpurities are present in the fluid being pumped.

GB2565579 discloses a pump that uses a liquid to form the pump blade andthereby addresses some of the problems above.

A liquid blade is by its nature deformable and can be distorted, anddistortion in the liquid blade can lead to leakage between the distortedportion of the blade and the solid surface of the rotor or stator towhich it should seal.

It would be desirable to provide a pump that is resistant to wear,offers low power consumption and a relatively small pumping mechanism,is relatively inexpensive to manufacture and operate and provides aneffective seal between the moving blade and static surfaces.

The discussion above is merely provided for general backgroundinformation and is not intended to be used as an aid in determining thescope of the claimed subject matter. The claimed subject matter is notlimited to implementations that solve any or all disadvantages noted inthe background.

SUMMARY

A first aspect provides a pump for pumping a gas, said pump comprising:

A rotor and a stator; one of said rotor or stator comprising at leastone liquid opening configured for fluid communication with a liquidsource; said liquid opening being configured such that in response to adriving force a stream of liquid is output from said opening, saidstream of liquid forming a liquid blade between said rotor and saidstator, gas confined by said stator, said rotor and said liquid bladebeing driven through said pump along a pumping channel from a gas inlettowards a gas outlet in response to relative rotational motion of saidrotor and said stator; wherein said pump is configured such that saidpumping channel comprises side walls that slope towards each other fromsaid rotor or stator that comprises said liquid opening towards afurther wall of said pumping channel remote from said rotor or statorcomprising said liquid opening, such that a distance between said sidewalls decreases with increasing distance from said liquid opening, atangent to a mid point of said side walls having an angle of between 5ºand 40º with respect to a line perpendicular to an axis of rotation ofsaid rotor.

The inventors of the present invention recognised that were the elementsof a pump to be configured with liquid opening(s) such that liquidoutput through the openings formed a surface or blade between theelements of the pump, then on rotation of one of the elements withrespect to the other, the liquid blade could be used to drive the gasthrough the pump.

Such a liquid blade is by its nature, deformable, low cost, andgenerally able to provide good sealing between surfaces of the trappedvolume without the need for tight manufacturing tolerances. Furthermore,such a blade is not subject to wear itself and provides very little wearon the surfaces that it contacts.

The blade is formed of a flowing liquid such that the liquid forming theblade is continuously replenished. A surface of the blade acts alongwith a surface of the elements to confine, trap, isolate or enclose thegas to be pumped. Relative rotation of the rotor and stator cause thetrapped gas to be moved from a gas inlet to a gas outlet along a pumpingpath or channel. Gas to be pumped is located on either side of theblade.

One problem to be addressed with such a pump is that the liquid blade isby its nature deformable and can be distorted, and this may lead toleakage between the distorted portion of the blade and a solid surfaceof the rotor or stator to which it should seal. In particular, it hasbeen found that there is tapering of the liquid sheet or blade away fromthe liquid opening(s) and thus, there is an opportunity for gas leakagebetween the side walls of the pumping channel and the edges of theliquid blade, particularly at radial distances remote from the liquidopenings where the cumulative effect of the tapering of the blade isgreater. This has been addressed by providing side walls to the pumpingchannel that are themselves tapered, so that they slope towards eachother to compensate for the tapering of the liquid blade, providing forimproved sealing along the edge of the liquid blade. In particular, ithas been found to be advantageous if the angle of the side wall isselected to be slightly greater than the angle of taper of the liquidblade such that there is not a gap between the blade and the side wall.

The angle of taper of a liquid blade will depend on the type of liquidand in particular, its surface tension and viscosity and on the speed ofrotation and the driving force pushing the liquid out through the liquidopenings.

In this regard, in operation a surface of the liquid blade comprises aradial dimension between said rotor and stator and an axial dimensionperpendicular to said radial dimension and parallel to an axis ofrotation. To compensate for the tapering of the blade, the pump isconfigured such that a dimension of said pumping channel parallel tosaid axial dimension of said liquid blade decreases with increasingradial distance from said liquid opening.

The angle of the side wall is configured to be similar to but slightlygreater than the predicted angle of taper of the liquid blade. It isconfigured such that a tangent to a mid point of the side walls have anangle of between 5^(º) and 40^(º) with respect to a line perpendicularto an axis of rotation of said rotor. Preferably between 8º and 25º morepreferably, between 10º and 15º.

The sloped angle is the angle of much of the side wall, in someembodiments, the middle section of the side wall is straight and slopedat this angle with curved sections at either end.

In some embodiments, said pump is configured such that said side wallsof said pumping channel flare outwards towards a junction with saidrotor or stator comprising said liquid opening.

In addition to the liquid blade tapering, there may also be distortionof the liquid blade where it first impinges on the sealing edges of theside walls of the pumping channel. This distortion and deviation fromits original path can be reduced by flaring the walls outwards such thatthe sealing gap for the liquid blade is smaller and any deviation has asmaller effect towards the edges. The flaring outwards means that thedistance between side wall increases close to and in a direction towardsthe junction between the stator and rotor, the flaring providing acurved side wall surface.

In some embodiments, said side walls are configured such that a junctionbetween each of said side walls and said further wall is curved.

There is additional disturbance and distortion of the liquid blade atthe junction between the further wall and the sloping edge of the sidewalls and this may be reduced and any potential leakage here inhibitedby the use of a curved surface at the junction. The further wall facesthe rotor and in some embodiments, is substantially parallel to the axisof rotation of the rotor at its mid point.

In some embodiments, said side walls are symmetrical about an axisperpendicular to a mid point of said further wall.

In some embodiments, said rotor comprises said liquid opening and ismounted to rotate within said stator.

Though all that is required is relative rotational movement between therotor and the stator, it may be advantageous if it is the rotor thatrotates and has the liquid openings as in some cases the rotation of therotor may provide an additional driving force to the liquid as it exitsthe openings and forms the blade. In this regard the rotor may in someembodiments, be a hollow cylinder rotationally mounted such that a lowerend extends into a liquid reservoir or sump. Rotational motion helpsdraw the liquid up the cylinder and expels it through the liquidopenings, the liquid forming a blade which on impact with the statorwall runs down the stator walls, along the pumping channel and iscollected in the sump to be reused.

In some embodiments, said liquid opening comprises at least one slit,extending longitudinally parallel to an axis of rotation of said rotor.

Although the liquid opening may have a number of forms, in someembodiments it comprises a slit which when liquid exits the slit forms asubstantially planar liquid blade. The slit may be angled with respectto the rotational axis but in some embodiments extends longitudinallyparallel to the axis of rotation of the rotor. In other embodiments,rather than being a slit, the liquid opening(s) may comprise a pluralityof openings arranged along a line.

In some embodiments, said rotor comprises a plurality of slits extendinglongitudinally parallel to an axis of rotation of said rotor atdifferent positions around an outer circumference of said rotor.

In some embodiments, said stator and rotor are configured such that saidpumping channel runs around a circumference of an inner one of saidrotor or stator, said gas inlet being arranged to be vertically higherthan said gas outlet in operation.

As the liquid that forms the liquid blade will, on hitting a wall of thepumping channel, run down it and collect in the base of the channel,there should be some way of draining the liquid from the pumping channelif the pumping channel is not to become full of liquid. In some cases,the pumping channel is configured such that the gas inlet is higher thanthe gas outlet when the pump is in operation such that the liquid willdrain out through the gas outlet. In some embodiments, the pumpingchannel runs around the circumference of the stator a single time, orrather slightly less than a whole turn around the circumference. Inother embodiments, the pumping channel may run around the circumferenceof the stator multiple times.

In some embodiments, a lower surface of said pumping channel at said gasoutlet is lower than a lower surface of said pumping channel at said gasinlet, and a higher surface of said pumping channel at said gas outletis higher than a lower surface of said pumping channel at said gas inlet

The liquid blade pushes the gas in a substantially circumferentialdirection along the direction of rotation of the rotor. Thus, it isadvantageous if the pumping channel and gas outlet are also arrangedalong this path. Thus, although the gas outlet should be below the gasinlet to allow draining of the liquid, it is advantageous if it is onlyslightly below the gas inlet such that gas is effectively driven by theliquid blade as it rotates.

In some embodiments, a cross sectional area of said pumping channel isconfigured to increase from said gas inlet to said gas outlet.

Although conventionally the cross-sectional area of the pumping channelmay decrease from gas inlet to gas outlet to provide some compression ofthe gas, in some embodiments, the cross-sectional area increases. Wherea liquid blade is used then the liquid that forms the liquid blade iscontinuously replenished, such that liquid collects within the pumpingchannel. Draining of the liquid from the pumping channel is required tomaintain a free volume for pumping gas, and the liquid while it iswithin the pumping channel will decrease the volume available for thegas being pumped. Thus, it may be advantageous to increase thecross-sectional area from gas inlet to gas outlet to avoid the pumpingchannel becoming too constricted by the liquid collecting within it.

In some embodiments, said pump is configured such that said increase incross sectional area from said gas inlet to said gas outlet and anamount of liquid supplied to said pump during normal operation areselected, such that although the overall cross sectional area increases,the cross sectional area available to gas decreases from said gas inletto said gas outlet and said gas being pumped is compressed.

It may be advantageous to design the pump so that the increasingcross-sectional area and amount of liquid supplied to the pump to formthe liquid blade in operation are linked so that the decrease in pumpingchannel volume that occurs due to the liquid collecting in the pumpingchannel can be compensated for to some extent by the increase incross-sectional area but in such a way that the cross-sectional areaavailable to the gas being pumped decreases slightly such that there issome amount of compression of the gas.

In some embodiments, the pump further comprises sealing means betweensaid side walls and said rotor or stator comprising said liquid opening.

In order to reduce leakage of gas and liquid, sealing means may beapplied between the side walls of the pumping channel and the rotor orstator comprising the liquid opening. In this regard, where the width ofthe pumping channel from gas inlet to gas outlet decreases, close to thegas inlet the liquid opening will extend beyond the width of thenarrower pumping channel and thus, providing sealing means to reduce theamount of liquid that exits the portion of the liquid opening(s) that donot open into the narrower channel close to the inlet is advantageous.

In some embodiments, said pump comprises a vacuum pump.

Further particular and preferred aspects are set out in the accompanyingindependent and dependent claims. Features of the dependent claims maybe combined with features of the independent claims as appropriate, andin combinations other than those explicitly set out in the claims.

Where an apparatus feature is described as being operable to provide afunction, it will be appreciated that this includes an apparatus featurewhich provides that function or which is adapted or configured toprovide that function.

The Summary is provided to introduce a selection of concepts in asimplified form that are further described in the Detailed Description.This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used asan aid in determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, withreference to the accompanying drawings, in which:

FIG. 1 shows a liquid blade in a pump according to an embodiment;

FIG. 2 shows a pump according to an embodiment; and

FIG. 3 shows a cross-section through a pumping channel of a pumpaccording to an embodiment.

DETAILED DESCRIPTION

Before discussing the embodiments in any more detail, first an overviewwill be provided.

Embodiments relate to a pump where the blade of the pump is formed by aliquid such as water that is expelled from one or more apertures in oneof the rotor or stator to form a sheet of water that acts as a blade forpushing the fluid to be pumped through the pump. Relative rotation ofthe stator and rotor cause the fluid to be urged from an inlet to anoutlet. When liquid is expelled from the apertures to form a sheet thistapers away from the apertures such that the sheet narrows. This cancause problems of fluid leakage around the edges of the sheet which actsas the blade. Embodiments address this by defining a similarly taperedshaped pumping channel such that the liquid blade adheres to the surfaceof the pumping channel walls and gaps are avoided or at least inhibited.

In some embodiments, discrete volumes of gas to be pumped are definedwithin a stator structure by an upper and lower sealing edge andvertical water sheets. These sealed volumes are then driven radiallyfrom the inlet to the outlet in a mechanism analogous to a rotary vanepump. One technical challenge is to maintain an effective gas sealbetween the water sheet and the sealing faces defined by the statorwalls. In one embodiment the pump comprises a hollow cylindrical rotorthat carries water up from a sump and out through vertical slits togenerating rotating sheets of water. As the water exits the slit the topand bottom edges of the sheet taper inwards towards the centre of thesheet as it travels out from the rotor to stator outer wall. This iscompensated for by appropriately sloping the upper and lower sealingedges of the pumping channel walls to match the tapering of the watersheet. In addition, where the sheet first impinges on the sealing edges,the leading edge, it is disturbed and deviates from its original path.This is addressed by introducing a suitable curvature to the slope atthe leading edge (inner diameter). It was also observed that at theouter diameter at the corner between the outer stator wall and thesloping edge additional disturbance to the water sheet occurred. This isaddressed by introducing a radius at this corner. This combinationdefines a unique, and novel, geometry for the stator channel .

FIG. 1 schematically shows the tapering of blade 40 formed of a sheet ofliquid expelled through liquid opening 12, which in this embodiment hasthe form of a slit formed in rotor 10, the edges of the slit definingeither edge of the blade 40. In this example, the tapering angle isshown as 20^(º) It should be understood that this angle may varydepending on both the length and the width of the aperture and the forcewith which the liquid is expelled through the aperture along with theviscosity and surface tension of the liquid. The liquid is in thisembodiment water.

FIG. 2 schematically shows a pump according to an embodiment. In thisembodiment, rotor 10 is mounted to rotate within stator 20. Rotor 10 hasa slit 12 through which water is expelled forming blade 40 such as isshown in FIG. 1 . As the rotor 10 rotates with respect to stator 20 theblade pushes gas around through the pumping channel 38 within stator 20from an inlet 52 to an outlet 54.

The base of inlet 52 is slightly higher than the base of outlet 54 whichallows liquid from the liquid blade that collects within the pumpingchannel 38 during the pumping of the gas, to flow from inlet 52 tooutlet 54 where it is exhausted.

In this embodiment, rotor 10 is a hollow cylinder and the centrifugalforce caused by rotation of the rotor causes liquid to rise up from asump and be expelled through liquid slit 12. In some embodiments, theremay be a pump to send water towards and through the slit 12.

The cross-sectional area of inlet 52 is smaller than the cross-sectionalarea of outlet 54 in this embodiment and this increase in crosssectional area from inlet to outlet helps compensate for the decrease inavailable volume for any fluid or gas being pumped that occurs due tothe accumulation of the liquid from the liquid blade within the pumpingchannel 38. The side walls of the pumping channel 38 are sloped suchthat the cross section of the pumping channel tapers in a correspondingway to the liquid blade of FIG. 1 . This avoids or at least inhibitsgaps being formed between the side walls and the liquid blade towardsthe outer edges of the pumping channel, further from the rotor, wherethe tapering is most pronounced.

FIG. 3 shows a cross-sectional view of pumping channel 38 where the formof this channel can be seen more clearly. In this embodiment, the sidewalls 34 are sloped at an angle of 25^(º) when taken from a tangent atthe midpoint 34 b of the side walls. The side walls towards the rotor 34a have a more pronounced taper, such that they flare outwards in acurved manner and are further apart than they are towards the middle ofthe walls. The ends of the side walls 34 c towards the further wall 36are curved so that there are no sharp angles as the side walls curveround to form the further wall and disruptions in the flow are reduced.In this regard the side walls are those that extend substantiallyradially, while the further wall faces the rotor and runs substantiallyaxially, parallel to the axis of rotation.

In operation as the liquid exits the slit 12, the top and bottom edgesof the blade taper inwards towards the centre of the blade as it travelsout from the rotor towards the further wall 36. This tapering is matchedand compensated for by appropriately sloping the upper and lower sidewalls 34 of the stator that along with further wall 36 form the pumpingchannel 38. This tapering is designed to substantially match thetapering of the water sheet with slightly more taper to avoid or atleast reduce any gaps.

Additionally, where the sheet or blade first impinges on the side walls34 a it is disturbed and deviates from its original path. This isaddressed by introducing a suitable curvature to the slope of the sidewall adjacent to the leading edge 34 a such that the distance betweenthe side walls 34 is greater at this junction between rotor 10 andstator 20 and has a curved shape. It has also been observed that at theend 34 c of the side walls at the junction with the further wall 36additional disturbance to the liquid sheet occurs. This can be reducedby introducing a radius at this corner such that there is curvaturehere. In this way, the geometry and cross-section of channel 38 isadapted to the properties of the liquid sheet and provides effectivesealing for pumping gas.

As in this embodiment, the slit 12 is longer than the width of channel38 closer to the inlet, as the channel has a smaller axial dimensionhere, sealing means 32 are provided between the stator and rotor oneither side of the pumping channel, to avoid or at least inhibit liquidleakage from the pumping channel.

As can be seen from the cross section, the lower side wall slopesvertically downwards from the inlet to the outlet, such that liquidaccumulating in the pumping channel 38 drains at the outlet.

Although illustrative embodiments of the invention have been disclosedin detail herein, with reference to the accompanying drawings, it isunderstood that the invention is not limited to the precise embodimentand that various changes and modifications can be effected therein byone skilled in the art without departing from the scope of the inventionas defined by the appended claims and their equivalents.

Although elements have been shown or described as separate embodimentsabove, portions of each embodiment may be combined with all or part ofother embodiments described above.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are described asexample forms of implementing the claims.

1. A pump for pumping a gas, said pump comprising: a rotor and a stator;one of said rotor or stator comprising at least one liquid openingconfigured for fluid communication with a liquid source; said liquidopening being configured such that in response to a driving force astream of liquid is output from said opening, said stream of liquidforming a liquid blade between said rotor and said stator, gas confinedby said stator, said rotor and said liquid blade being driven throughsaid pump along a pumping channel from a gas inlet towards a gas outletin response to relative rotational motion of said rotor and said stator;wherein said pump is configured such that said pumping channel comprisesside walls that slope towards each other from said rotor or stator thatcomprises said liquid opening towards a further wall of said pumpingchannel remote from said rotor or stator comprising said liquid opening,such that a distance between said side walls decreases with increasingdistance from said liquid opening, a tangent to a mid point of said sidewalls having an angle of between 5° and 40° with respect to a lineperpendicular to an axis of rotation of said rotor.
 2. The pumpaccording to claim 1, wherein said side walls are sloped such that saidangle of a tangent to a mid point of said side wall with respect to aline perpendicular to an axis of rotation of said rotor, is between 8°and 25° preferably, between 10° and 15°.
 3. The pump according to claim1, said pump being configured such that said side walls of said pumpingchannel flare outwards towards a junction with said rotor or statorcomprising said liquid opening.
 4. The pump according to claim 1, saidpump being configured such that a junction between each of said sidewalls and said further wall is curved.
 5. The pump according to claim 1,said side walls being symmetrical about an axis perpendicular to a midpoint of said further wall.
 6. The pump according to claim 1, whereinsaid rotor comprises said liquid opening and is mounted to rotate withinsaid stator.
 7. The pump according to claim 1, wherein said liquidopening comprises at least one slit, extending longitudinally parallelto an axis of rotation of said rotor.
 8. The pump according to claim 1,wherein said stator and rotor are configured such that said pumpingchannel runs around a circumference of an inner one of said rotor orstator, said gas inlet being arranged to be vertically higher than saidgas outlet in operation.
 9. The pump according to claim 8, wherein alower surface of said pumping channel at said gas outlet is lower than alower surface of said pumping channel at said gas inlet, and a highersurface of said pumping channel at said gas outlet is higher than alower surface of said pumping channel at said gas inlet.
 10. The pumpaccording to claim 1, wherein a cross sectional area of said pumpingchannel is configured to increase from said gas inlet to said gasoutlet.
 11. The pump according to claim 10, wherein said pump isconfigured such that said increase in cross sectional area from said gasinlet to said gas outlet and an amount of liquid supplied to said pumpto form said liquid blade in normal operation are selected such that across sectional area of said pumping channel available to gas decreasesfrom said gas inlet to said gas outlet and said gas being pumped iscompressed.
 12. The pump according to claim 1, further comprisingsealing means between said side walls and said rotor or statorcomprising said liquid opening.
 13. The pump according to claim 1, wheresaid pump comprises a vacuum pump.